[R] Overlay two plots on the same device with axes having the same scale.

[John Sorkin]

R 2.6.0 
Windows XP

I have crated a file containing data with x and y values and have plotted the data using the output of gam. I would like to overlay an x,y plot of the data on top of the line returned by gam. I have succeeded in doing this using par(new=TRUE), unfortunately the y axis of the overlayed plots are of slightly different scale. How can I set the axes of the overlay plots so the scales are exactly the same?

y<-matrix(nrow=200,ncol=2)

# Create data
y[1:200,2]<-sin((0:99)/(0.5*10*pi))+rnorm(100,0,.2)
y[,1]<-1:200

# Plot of raw data.
plot(y[,1],y[,2])
oldpar<-par(new=TRUE)
fit1<-gam(y[,2]~s(y[,1]))
#Plot of fit - overlays plot of raw data. 
#Note scale of overaly is not the same as the original raw data plot.
summary(fit1)
plot(fit1)

Thanks,
John


John David Sorkin M.D., Ph.D.
Chief, Biostatistics and Informatics
University of Maryland School of Medicine Division of Gerontology
Baltimore VA Medical Center
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524
(Phone) 410-605-7119
(Fax) 410-605-7913 (Please call phone number above prior to faxing)

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